The long-range objective of this research is to develop a theory of the interactions among vocal fold motion, laryngeal airflows and air pressures, and the generation and propagation of acoustic signals in the vocal tract. This theory will extend our knowledge well beyond the linear source-filter theory, which has been the mainstay of speech and voice science for half a century. Models of the mechanics of phonation will continue to be developed that will result in predictive equations and visual illustrations that lead to deeper clinical insight into normal and abnormal phonatory processes. The research will be conducted using three complementary phonatory models --excised canine larynges, an artificial vibrating mechanical larynx, and a computational model. The specific aims for this funding period are: (1) To develop a computer simulation of pulsatile airflow and acoustic wave propagation in the models of vocal tract and glottal airway; (2) To quantify turbulence in the glottal flow and its acoustic effects; (3) To parameterize the pressure-flow relationship in the larynx; (4) To investigate the effect of glottal adduction and vocal fold geometry on the acoustic vocal efficiency of the larynx; (5) To investigate the effects of left-right asymmetry of the vocal folds (geometrical or mechanical) on the aerodynamic and acoustic output of the larynx; and (6) Using a previously developed computer model of phonation, to contrast the effects of active versus passive properties of vocal fold tissue on aerodynamic, kinematic, and acoustic characteristics of phonation.